This invention relates to a process for producing micropatterns on large-area substrates, especially liquid crystal displays, in which patterns are transferred from at least one mask onto a substrate by optical means. This process can furthermore be used in inspecting micropatterns on large-area substrates. Micropatterns on large-area substrates are required primarily for liquid crystal displays. The invention furthermore relates to an apparatus for the carrying out of the claimed process.
The art of liquid crystal displays has reached a high level, and there are already many applications, such as automobile dashboard displays or the screens of portable computers, and, in particular, liquid crystal displays offer a promising technology for the replacement of the TV cathode-ray tubes still commonly used today. There are some technological difficulties facing the growing interest in such large-area displays, and they will be explained below.
Liquid crystal displays are manufactured by lithographic methods, according to which patterns are transferred from at least one mask--often up to ten masks--to a substrate, such as a glass plate, for example. The transfer is usually performed by an optical method in which beams from a light source or laser beams project the patterns of the mask onto a photosensitive coating on the substrate, and the pattern is then fixed on the substrate by etching or other such methods in additional process steps. As the size of the displays increases, the optical means containing lenses or mirror systems become correspondingly larger and more unwieldy, and the difficulty of making them increases considerably. Furthermore, imaging errors must be expected, so that accuracy requirements can no longer be satisfied, and very small patterns of the order of 4 micrometers or even 1 micrometer can no longer be used. Large-area displays, with a length on each side of at least 10 cm, or advantageously 20 cm and more, cannot be satisfactorily produced by the methods common today, which appear entirely feasible for smaller displays.